Limit switch for rising stem gate valves

ABSTRACT

A limit switch assembly for a rising-stem valve includes an operating lever actuator element mounted to an outer end of an actuator arm. An electrical switch mounted adjacent the outer end has an operating lever. When the actuator arm is in an outward position, the operating lever actuator element retains the operating lever in a first position wherein the electrical switch is in a first state, and when the actuator arm is in an inward position the operating lever is in a second position wherein the electrical switch is in a second state. An adjustment nut is mounted to the outer end adjacent the operating lever actuator element, and the operating lever actuator element and the adjustment nut are configured to be adjusted along a longitude of the actuator arm to change a distance the operating lever actuator element must travel to move the operating lever into the first position.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/124,662, entitled “Limit Switch for Rising Stem GateValves”, filed Sep. 7, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/686,401, entitled “Limit Switch for Rising StemGate Valves”, filed on Aug. 25, 2017, and now issued as U.S. Pat. No.10,088,073. The aforementioned applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention pertains to the field of valves. More particularly, theinvention pertains to limit switches for rising-stem type valves.

Description of Related Art

Gate valves are often used in fire protection applications to close offwater mains. Referring to FIG. 1, such valves have a valve body 4 withflanges on an inlet side 5 and outlet side 6. A gate 8 fits in a channel7 inside the valve body 4. When the gate 8 is fully lowered into thechannel 7 water flow from inlet 5 to outlet 6 is blocked. When the gate8 is raised, water can flow freely through the body 4. The gate 8 isactuated by a stem 9, which has a threaded portion 10 near the upper endand a non-threaded portion 11 between the threaded portion 10 and thelower end which is coupled to the gate 8 by a swivel which allows thestem 9 to turn while the gate 8 is prevented from swiveling by thechannel 7. The stem 9 extends upward through valve cover 2, which ismounted on the valve upper flange 3. A yoke 1 guides the stem 9 to thevalve hand wheel 13, which is held on the end of the stem 9 by a holddown nut 14.

In rising-stem type valves, when the gate 8 is raised or lowered, theentire stem 9 moves upward or downward through the yoke 1 as thethreaded part 10 of the stem 9 threads through the yoke nut 12 on thetop of the yoke 1.

In some systems it is necessary to be able to determine remotely if thevalve is open or closed. For example, in a fire-protection sprinklersystem, it is important that all of the mains valves be open so that thesprinklers can protect the sprinkled area, and it is desirable that afire alarm system which monitors flow in the sprinkler system to detectactuation should also be able to warn if the sprinklers were shut off bymanual operation of the valves.

On a ball valve system, it is relatively easy to tell if the valve is onor off, since the valve actuator lever will either be in the openposition (usually parallel with the pipe) or the closed position(usually perpendicular to the pipe). A switch can be mounted to closewhen the lever is in the open position, to signal the readiness of thevalve to a remote system.

In a gate valve, the hand wheel 13 must be turned many times to fullyraise or lower the gate 8, and there is no one “on” or “off” position ofthe wheel 13. In the prior art, installers have mounted an after-marketsupervisory or limit switch, such as the OSYSU series supervisoryswitches made by Potter Electric Signal Company in St. Louis, Mo. to theyoke 1, to provide the monitoring switch signal for the monitoringsystem. The switch is mounted with a clamp or U-bolts or the like to theopen side of the yoke 1 at a position chosen by the installer, with atrip rod from the switch riding on the side of the stem 9 of the valve.During installation, after mounting the switch, the valve is operated tothe fully open position, and the installer marks the stem 9 where thetrip rod hits the stem 9. The installer then removes the switch andmanually files a groove in the stem 9 where he marked it. The switch isthen re-mounted at the same spot as before, so that the trip rod dropsinto the filed groove and actuates the switch.

SUMMARY OF THE INVENTION

In an embodiment of the invention, a limit switch assembly for arising-stem valve having a stem with a diameter and a groove marking adesired stem position, includes: an actuator arm having an inner end andan outer end, the inner end of the actuator arm forming a follower; anoperating lever actuator element mounted to the outer end of theactuator arm; an electrical switch having an operating lever, theelectrical switch mounted adjacent to the outer end of the actuator armsuch that when the actuator arm is in an outward position the operatinglever actuator element contacts and retains the operating lever in afirst position such that the electrical switch is in a first state ofoperation, and when the actuator arm is in an inward position theoperating lever is in a second position such that the electrical switchis in a second state of operation; a bias spring biasing the actuatorarm toward the inward position; and an adjustment nut mounted to theouter end of the actuator arm adjacent the operating lever actuatorelement, the operating lever actuator element and the adjustment nutconfigured to be adjusted along a longitude of the actuator arm tochange a distance the operating lever actuator element must travel inorder to put the operating lever in the first position.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an exploded view of a gate valve.

FIG. 2 shows a cut-through view of the yoke for a gate valve with thestem in a lowered position and the limit switch disengaged with a groovearound the stem.

FIG. 3 shows a cut-through view of the yoke for a gate valve with thestem in a raised position and the limit switch engaged in a groovearound the stem.

FIG. 4 shows a top view of a first embodiment of the actuator arm of thelimit switch.

FIG. 5 shows a top view of a second embodiment of the actuator arm ofthe limit switch.

FIG. 6 shows a cut-through view of the yoke for a gate valve with thestem in a raised position and the limit switch engaged in a groovearound the stem, in another embodiment of the limit switch.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the parts of the valve which are conventional werediscussed in the background section, above. The novel valve has amounting platform 17 formed into the side of the yoke 1 for mounting thelimit switch assembly 16. Alternatively, there could be a separatemounting plate which mounts the switch 16 to the yoke 1 with screws orthe like. A hole 18 is bored through a side of the yoke 1, through whichthe actuator rod 22 and bracket 20 can extend inside the interior of theyoke 1.

FIG. 4 shows a view of a first embodiment of the actuator arm 22. On theouter end of the actuator arm 22, a radius washer 25 is held on by a nut26 threaded onto the arm 22. A bracket 20 in this embodiment isU-shaped, with an outer leg 33, inner leg 34 mounted to the inner end ofthe actuator arm 22, and a base 35 between the inner leg 34 and outerleg 33. The inner leg 34 can be mounted in a permanent fashion bypress-fit, or by welding or brazing, in which case hole 18 would need tobe large enough to pass the bracket 20. Alternatively, the inner end ofthe actuator rod 22 could be threaded into a threaded hole in the innerleg 34 of bracket 20, in which case the hole 18 would only need to belarge enough to pass the actuator rod 22, and the bracket 20 would beassembled onto the actuator rod 22 after the switch 16 is mounted on theyoke 1. A follower 21 is provided on the inside of the outer leg 33 ofthe U-shaped bracket 20. The base 35 is made larger than the diameter ofthe stem 9, at least large enough so that the stem 9 fits between theinside arm 34 and the follower 21 on the inside of the outside arm 33.The length of the inside arm 34 and the outside arm 33 is at leastone-half of the diameter of the stem 9, so that when the bracket 20 isaround the stem 9, the follower 21 contacts the side of the stem 9opposite the actuator arm 22.

FIG. 5 shows a view of a second embodiment of the actuator arm 22. Thisembodiment differs from the embodiment in that the actuator bracket 20is a closed form, shown in FIG. 5 as a rectangle, although it could beround or some other shape. FIG. 5 also shows an embodiment in which thefollower is in the form of a roller 42 mounted on an inside surface 43of the bracket 20.

FIGS. 2 and 3 show a cut-through view of the valve yoke 1, with the stemnut 12 at the top of the yoke 1. The threaded portion 10 of the stem 9is threaded into the stem nut 12, so that turning the stem 9 causes thestem 9 to be moved up and down, raising and lowering the gate 8 withinthe valve. It will be understood that the threaded portion 10 and gate 8are truncated in these figures for illustrative purposes.

A circumferential groove 15 is formed around the unthreaded portion 11of the stem 9, at a location along the length of the stem 9 selectedsuch that when the gate 8 is in the desired position (either open orclosed or some other selected position), the groove 11 is aligned withthe center of the hole 18. It will be understood that more than onegroove 15 could be formed, to allow a valve to have more than onedesired position—for example, both an “open” and a “closed” position.

In the embodiment of FIG. 2, the limit switch assembly 16 is shownmounted to the side of the yoke 1 on a mounting plate 29 fastened to theside of the yoke 1 by screws 30. The base plate 32 of the limit switchassembly 16 is mounted to the yoke 1 by means of a mounting boss or tube31, held to the inside of the yoke 1 by a nut 23.

FIG. 3 shows a different arrangement for mounting the limit switchassembly 16, in which the mounting plate 29 is replaced by a pluralityof feet 40, which are of differing sizes to accommodate the taper andcircular shape of the yoke 2. In this arrangement, screws 46 can beprovided to hold switch cover 45 on the base plate 32.

With the limit switch assembly 16 mounted on the yoke 1, whether to amounting platform 17 as shown in FIG. 1, or using a mounting plate 29 asshown in FIG. 2, or with feet 40 as in FIG. 3, the actuator arm 22passes through the center of the hole 18, with the bracket 20 around thestem 9. A bias spring 24 presses on the base plate 32 and the radiuswasher 25 to bias the actuator arm 22 outward from the yoke 1, pressingthe follower 21 against the side of the stem 9. An electrical switch 27is mounted inside the limit switch assembly 16 in a location such thatthe operating lever 28 of the electrical switch 27 is operated by theradius washer 25 when the actuating arm 22 is in an outward position,and is not operated by the radius washer 25 when the actuating arm 22 isin an inward position.

The electrical switch 27 can be, for example, a miniature switch(commonly called a “microswitch”) as made by Honeywell and many othermanufacturers. The electrical switch 27 can be of any electrical kindrequired by the application, for example a single-pole-double throw(SPDT) type, which would have a normally-open (NO) terminal, anormally-closed (NC) terminal, and a common terminal, such that when theswitch is operated the common terminal is connected to the NO terminal,and when the switch is not operated the common terminal is connected tothe NC terminal. This would permit the limit switch to be used withsystems which require either contact closure or contact opening at thedesired position, although it will be understood that other contactarrangements can be used within the teachings of the invention.

FIG. 2 shows the valve with the gate 8 and stem 9 in a position otherthan the desired position. In this position, the follower 21 rides onthe side of the unthreaded portion 11 of the stem 9 under the force ofthe bias spring 24. This holds the actuator arm 22 in an inwardposition, such that the radius washer 25 does not operate the operatinglever 28 of the electrical switch 27. If an SPDT type of switch 27 wereused, in this position there would be a closed circuit between the NCterminal of the electrical switch 27 and the common terminal, and anopen circuit between the NO terminal and the common terminal.

When the stem 9 and gate 8 are moved to the desired position (shown inFIG. 3 as a raised, valve-opened position), the follower 21 on thebracket 20 of the actuator arm 22 is pulled by the force of the biasspring 24 to drop into the groove 15. This moves the actuator arm 22 toan outward position, in which the radius washer 25 contacts operatinglever 28 to operate electrical switch 27. If an SPDT type of switch 27were used, in this position there would be a closed circuit between theNO terminal of the electrical switch 27 and the common terminal, and anopen circuit between the NC terminal and the common terminal.

FIG. 6 shows a cut-through view of the yoke for a gate valve with thestem in a raised position, and the limit switch engaged in a groovearound the stem, corresponding to FIG. 3. In this embodiment, theactuator arm 61 of the limit switch is biased toward the stem 9 by biasspring 24, rather than away from the stem as shown in FIGS. 2-5. Thefollower 60 is formed by the end of the actuator arm 61, so that whenthe follower 60 drops into groove 15, the switch 27 is operated.

Accordingly, it is to be understood that the embodiments of theinvention herein described are merely illustrative of the application ofthe principles of the invention. Reference herein to details of theillustrated embodiments is not intended to limit the scope of theclaims, which themselves recite those features regarded as essential tothe invention.

What is claimed is:
 1. A limit switch assembly for a rising-stem valvehaving a stem with a diameter and a groove marking a desired stemposition, comprising: an actuator arm having an inner end and an outerend, the inner end of the actuator arm forming a follower that followsthe stem; an operating lever actuator element mounted to the outer endof the actuator arm; an electrical switch having an operating lever, theelectrical switch mounted adjacent to the outer end of the actuator armsuch that when the actuator arm is in an outward position the operatinglever actuator element contacts and retains the operating lever in afirst position such that the electrical switch is in a first state ofoperation, and when the actuator arm is in an inward position theoperating lever is in a second position toward the stem relative to thefirst position such that the electrical switch is in a second state ofoperation; a bias spring biasing the actuator arm toward the inwardposition; and an adjustment nut mounted to the outer end of the actuatorarm adjacent the operating lever actuator element, the operating leveractuator element and the adjustment nut configured to be adjusted alonga longitude of the actuator arm to change a distance the operating leveractuator element must travel in order to put the operating lever in thefirst position.
 2. The limit switch assembly of claim 1, wherein thefirst state of operation is a state of activation, and the second stateof operation is a state of inactivation.
 3. The limit switch assembly ofclaim 1, further comprising a base plate having a plurality of feet tomount the base plate on an exterior of a valve yoke.
 4. The limit switchassembly of claim 1, further comprising a base plate configured to mountto an exterior of a valve yoke, the base plate having a wedge shape. 5.The limit switch assembly of claim 1, further comprising a mounting bossand a mounting plate, the mounting boss configured to be secured to aninside of a valve yoke, to extend through a side of the valve yoke, andto attach to the mounting plate, the mounting plate configured to attachto an exterior side of the valve yoke.